2002 1.2 petrol Fiat Punto rough idle - (coil voltage fault)

[DIYspanner]

My nephew's Punto packed in this morning 500 yards from home.

I had a look at it this afternoon and although it started straight away, its seems to have a rough tick over.

I took a spark plug out and the cap was covered in rust so I've bought a new set of plugs and leads to keep the job right - probably fit them tomorrow.

In the shop, they told me the two ignition coils on the Puntos are vulnerable.

Anyone got experience with a poor running Punto?

 

[Burnerman]

Indeed they are, Mr. Spanner......a faulty coil pack will make the engine shake badly on tickover and tend to stall.
Revving the engine and things are less noticeable. Its best to fit a new set of plugs at the same time, too.
Usually the engine management light is illuminated on the dash when this happens.
John

 

[DIYspanner]

Most obliged Burnerman

I'll fit the plugs and leads and see how it runs then.

Faulty ignition coils will be considered after that.

 

[DIYspanner]

Problem identified.


One of the twin ignition coils is not being fed so there's only 1/2 an engine running.

Swapping plug leads and coil feeds round identified the fault and both coils are working.

The coil feeds go into the engine harness.


Can anyone point me to the other ends of the cables please so I can get it sorted out?


Thanks

 

[Spark123]

The other end of the wires is probably the ECU. It may be worth dropping the battery overnight to see if it just needs a reset.
Bad news is new ECUs aren't that cheap and I think they may be vehicle coded so a second hand one from a scrap yard don't work.

 

[Dave54]

Don't know if this helps. I bookmarked the site ages ago as being possibly useful.

Looking at the Fiat page it looks as if the ECUs give just the fault you describe.
http://www.ecutesting.com/fiat_punto_ecu_1_2_year_2000_-.html

 

[Burnerman]

Looks like a good site, Dave. I'll bookmark that one too.
John

 

[DIYspanner]

Most obliged folks.

As suggested by ecutesting.com, new coils and ECU.

I can get the coils from ebay

http://www.ebay.co.uk/itm/2x-Fiat-P...arts_Vehicles_CarParts_SM&hash=item1e84924c22

ECU is fitted to the back of the throttle housing apparently.


Anyone know why an ignition coil should start spiking? ... breakdown in insulation perhaps?

 

[Spark123]

Suppression or amplifier failure at a guess, allowing the collapsing emf (1000s of volts) to get to the ECU on a control voltage line.

 

[Mursal]

Snubber network failure so the current just jumps across the semiconductor switch (probably transistor), popping the junction.

 

[DIYspanner]

The engine management warning light is on at present so that should go out with a new ECU and ignition coils.

 

[DIYspanner]

New ECU and coils were fitted today and the engine ticks over and runs canny.

Sadly, the engine management light is still on and the seller of the ECU has suggested buying this to sought it out


http://www.ebay.co.uk/itm/221531025...l?_from=R40&_sacat=0&_nkw=221531025018&_rdc=1

 

[Burnerman]

The scanner will tell you what fault code it is, and will allow you to turn the lamp off.......let's hope it stops off!
John

 

[Dave54]

Glad to hear it's running OK.
I bought the orange one underneath "People also viewed" Worked OK with Saxo and cheaper than the garage.

 

[DIYspanner]

Glad to hear it's running OK.

So is my nephew, many thanks.

I bought the orange one underneath "People also viewed" Worked OK with Saxo and cheaper than the garage.

The £10.45 one or the £29.98 one ?


Never actually used a diagnostics scanner. It plugs in to a master plug I understand but how do you clear a fault once identified ?